Common cargo carrying pallets are well known to those of reasonable skill in the art and can be used for moving large and/or heavy loads. One disadvantage of cargo carrying pallets is poor mobility. In many cases a forklift or forktruck is required to maneuver the carrying pallet from one location to another. Providing the carrying pallet with wheels to enhance mobility of the pallet can result in increased mobility of the carrying pallet; however, providing wheels on the pallet can also result in a high load bearing concentration between the wheel(s) of the pallet and the floor, be it a factory concrete floor, asphalt driveway, earth, or the floor of an aircraft cargo area. As a direct result of the high load bearing concentration, the floor can be physically damaged or prematurely worn.
Further, for tire-like wheels, the load carrying strength of a pallet with wheels tends to be limited by both the bearing strength of the tire material and the tire pressure of the wheels; i.e., the maximum contact pressure along an area of contact between a wheel and a surface it is traveling over is roughly equivalent to the tire pressure. Tire-like wheels have some ability to “deform” or compress to help distribute weight, but to carry very heavy loads, very large tires with large diameters may be required to have the larger contact areas that can potentially expand upon compression. A cargo carrying pallet with such large tires tends to sit fairly high off the ground, which can be less stable and also can be a disadvantage in environments (e.g., ship hulls, aircraft cargo areas, truck cargo carrying areas, fitting under doorways, etc.) where space is limited.
Another apparatus used to move large and/or heavy loads is a frame or so-called “skate” or “dolly” to which one or more rollers are mounted. Handles connected to the frame enable it to be pushed or pulled along a floor. For example, Hillman Rollers, of New Jersey manufactures frames that employ multiple-roller load bearing mechanisms and assemblies. Most of the roller systems available from Hilman are all steel (although some are nylon), and operate based on the principle of the recirculating chain. This chain is constructed with a series of connected rolls that recirculate around a central load plate set into a framework. The frame acts only to hold the load plate in place, and can include a top plate to ease connection to the load. The rolls spread the load evenly on the load surface providing a low friction, controllable, high capacity moving device.
Although the frame plus roller approach effects some improvement in load distribution (as compared with, a wheel attached to a conventional pallet) by creating a surface interface consisting of several lines of contact, disadvantages still persist. The rollers themselves, as well as the recirculating chain, can collect dirt and debris. On rough surfaces, the lines of contact between the rollers and the rough surface can diminish virtually to merely points of contact, which can cause some rollers to lose all contact with a surface and put stress on the rollers remaining in contact. Known frame/roller systems are also disadvantageous in situations such as abrupt changes in surface inclination (such as transitions onto and off of ramps) or any other forms of surface imperfection, such as small rocks on or cracks in a surface over which the roller is traversing. Further, rollers made of materials like steel are capable of causing permanent damage to flooring such as aluminum (often found in aircraft) or linoleum and vinyl (often found in commercial storage areas).
Another limitation of known systems for moving loads is compatibility with different types of interfaces and loading systems, some of which may be at different elevations. For example, a load may need to be transported between rails and an aircraft, or a tarmac and an aircraft, a dock and a vessel, etc., and these different interfaces may not be compatible with a given pallet system. Systems usable on flat surfaces may be incompatible with rail based systems (and vice versa). Some systems may be constrained to specific domains of motion and cannot, for example, be dragged across a tarmac or other surface. An additional problem is the heavy weight and/or materials used in many transport systems often can cause damage to and/or reduce the working life of the surfaces being traversed, especially when a load is heavy or experiences vertical motion or shock (e.g., when an aircraft lands, when a load is being carried by a vehicle or other conveyance that is traversing over an irregular surface, such as a bump, choppy water, etc., traverses over a bump, etc.).